Many reactors applied to an in-vehicle booster circuit employ a structure in which a coil is wound around a resin-made bobbin disposed around a core, those are retained in a metal casing, and a filler is filled in the casing and is let cured.
Among those reactors, there is known a type which combines multiple divisional core pieces to form an annular core, and has coils wound around the right and left core legs. Each divisional core piece is embedded in a resin, and the resin portion serves as the covering portion of the core and the bobbin for the coils. In order to dispose a resin around the core, in general, molding is applied.
In addition, according to this type of reactor, a bus bar is connected to an end of the coil, and a wiring for a connection with an external device of the reactor is attached to a screw hole by screwing provided in the tip of the bus bar. That is, it is difficult to directly connect a wiring like a covered electric wire to an end of the coil formed by letting a wire like a rectangular wire to be wound around such a coil. Accordingly, the bus bar is connected to the end of the coil by welding, etc., a screw hole is provided in the tip of the bus bar, and a wiring and the bus bar are connected, or a connector provided at the wiring side is press-fitted to or engaged with the end of the bus bar.
Conventionally, the bus bar connected to the coil end is embedded in, together with a clamp (referred to as a stay) to fastening the core and the reactor to the casing, the interior of the resin-molded body integrally molded with the bobbin where the coil is wound by molding. In order to form a reactor, a coil wound in a cylindrical shape is attached to the outer circumference of the bobbin of this resin-molded body, and with the end of the coil and the bus bar embedded in the resin-molded body being in contact with each other, both are welded.
According to this type of reactor, when a high current continuously flows, the coil is heated, and the electric characteristic decreases. Hence, the internal temperature is measured through a temperature sensor like a thermistor, and an electrical conduction is controlled so as not to cause the coil to be heated to equal to or greater than a predetermined temperature.
When the reactor is provided with a sensor, in order to detect a temperature precisely, it is necessary to dispose the sensor near the coil and the core which generate heats. Accordingly, as disclosed in JP 2010-203998 A and JP 2012-243913 A, a structure in which the sensor is disposed between the right and left coils is employed. According to such conventional technologies, since the sensor is disposed at the center of the reactor, there is an advantageous effect that the detection precision of the temperature is excellent.
Meanwhile, according to a reactor including this type of sensor, a connector is necessary which connects the lead wire from the sensor with the wiring inside a vehicle. This connector needs a dimension to some level so as to ensure the insulation at the connected portion and to facilitate a manual connection work. While at the same time, it is necessary to fasten the connector using some holder so as not to move due to vibration, etc.
According to the reactor having the above-explained core embedded in the resin by molding, as a connector holder of this type, it is simple if a protrusion or a recess which catches the connector is provided in the resin portion. When, however, molding is performed, depending on the shape of a mold to be utilized, and the position and shape of the core to be disposed inside the resin portion, the position and shape of the holder are restricted.
In addition, the shape of the mold becomes complex when merely molding the cylindrical bobbin with the resin-molded body in an integral manner. Still further, the structure of the resin-molded body becomes complex when the core, the stay, and further the bus bar are embedded in the resin-molded body, making the manufacturing difficult. Yet further, when the reactor is connected with an external device, it is necessary to draw wirings in various directions depending on the position, shape, and size of the external device to be connected. When, however, the bus bar is embedded in the resin-molded body, the position of the bus bar is limited to the location where the bus bar is embedded in the resin-molded body only. Therefore, it is difficult to draw the bus bar in optional directions, such as the front, rear, right and left of the reactor.
In particular, since the bus bar supplies power to the coil, it is necessary to ensure a sufficient insulation against the core and the stay, etc., but when the bus bar, the core, and the stay are present in the same resin-molded body, for the purpose of the insulation among those pieces, it is necessary to make the resin-molded body thickened, resulting in an increase in the size of the resin-molded body, and an increase in the apply amount of the resin.
In addition, according to this type of reactor, when a high current continuously flows, the coil is heated and the electric characteristic decreases. Moreover, it becomes beyond the withstand temperature of the material, and the reliability is deteriorated. Accordingly, the internal temperature is measured through a temperature sensor like a thermistor to perform an electrical conduction control so as not to cause the coil to be heated to equal to or greater than a certain temperature. When the reactor is provided with a temperature sensor, it is necessary to dispose the sensor near the coil and the core which generate heat to precisely detect a temperature. Conversely, it is necessary to provide a sensor connector for the reactor to transmit detections signals from the sensor to the external device.
According to conventional technologies, since it is difficult to obtain a sufficient space, it is difficult to provide a connector itself at all, the connector is fastened to the exterior of the reactor, or a hook is provided at a largely projected portion of the resin-molded body from the casing to fasten the connector. However, since the core, the stay, and the bus bar, etc., are embedded in the resin-molded body, it is necessary to provide a holder so as not to interfere therewith, and thus the disposition of the connector is restricted.
The reasons of those problems will be explained with reference to a conventional reactor illustrated in FIGS. 13 and 14. According to this type of reactor, bobbins 102 are provided at respective outer circumferences of the right and left core legs of an annular core 101, and coils 103 are wound therearound. The yoke portion of the core 101 where no coil 103 is wound is covered over by a covering portion 104 integrally molded with bobbins 102. A support plate 105 to hold a sensor is integrally provided with the bobbins 102 between the right and left bobbins 102. A catch 106 to hook up lead wires of the sensor is provided at the portion of the covering portion 104 near the bobbins 102.
According to this type of reactor, in order to dispose the bobbins 102 around the core 101, in general, the core 101 is placed in a mold, and molding is applied which fills a resin to the interior of the mold around the core 101 and lets the resin cured. In this case, when there is a space between the mold surface and the core 101, the resin enters such a space, becoming burrs after the molding. In particular, according to the conventional technologies, the core 101 is caused to be in contact with the bottom of an aluminum-made casing 108 that retains thereinside a reactor to directly dissipate heat from the core 101. Hence, when burrs are present, a gap is formed between the casing 108 and the core 101. Accordingly, the heat dissipation performance deteriorates. Therefore, according to the conventional technologies, the core 101 is pushed by a spring from the upper space thereof to eliminate a space between the mold surface and the core 101, thereby suppressing a formation of burrs.
As explained above, to push the core 101 from the upper space thereof, it is necessary to let the spring to be in contact with the core 101. Accordingly, it is difficult to fill the resin on the upper face of the core 101. According to the conventional technologies, an opening 107 where no resin is present is formed on the upper face of the covering portion 104 covering the core 101 to position the core 101 in the mold. When, however, the opening 107 is present on the upper face of the core 101, it is difficult to provide the holder of a connector, the stay, and the bus bar, etc., in this location, and thus the holder is provided at a part of the casing 108 that retains thereinside the reactor, the holder is formed using a resin so as to project from the side of the core 101, and making a part of the resin-molded body be projected to a side, and, each component is disposed at the projected part.
The holder provided at a side of the core 101 increases the dimension of the reactor in the horizontal direction, disturbing a downsizing. In addition, the conventional technologies that push the core against the mold surface when a resin is filled needs to additionally provide a pushing mechanism together with the mold, and makes the structure of the mold complex. Hence, it is not suitable.
Likewise, when a part of the resin-molded body is projected to a side, the dimension of the reactor in the horizontal direction increases by what corresponds to the projection, which disturbs a downsizing of the reactor. In addition, the position where the bus bar and the holder of the connector can be disposed is restricted. In particular, among the conventionally well-known reactors, there is a type that draws a drawn part 103a of the coil end from the yoke-side of the core. According to this type of reactor, when ends of the coil 103 are drawn from the two yoke sides, respectively, opposite to each other, the drawn part 103a interferes with the disposition of the bus bar and the connector on the upper face of the covering portion 104.
The present disclosure has been made to address the aforementioned technical problems of the conventional technologies. The present disclosure integrally forms a holder by a resin on the upper portion of a core to enable a downsizing of a reactor, and eliminates the necessity of a work of pushing the core against a mold surface, thereby simplifying a resin molding work and the structure of the mold.
In addition, the present disclosure reduces the number of components embedded in a resin-molded body including a core to simplify the resin-molded body and the structure of the mold thereof, to simplify a manufacturing process associated therewith, and to downsize a whole reactor.
Still further, the present disclosure ensures a leeway for the degree of freedom for a disposition of a terminal stage, and an excellent insulation performance, and enables a disposition of the holder of a connector of an electronic component like a temperature sensor in an arbitrary location on the reactor.